There are widely known mercury of mercury-wetted contacts for switching devices, comprising a solid metal base made of platinum, iron, nickel, or metals of the chromium subgroup, viz. tungsten, molybdenum, as well as the methods of manufacturing of such contacts, including wetting the cleaned and degreased solid metal base(made of iron and nickel) with mercury by periodic dipping of the base into a mercury-containing liquid medium.
The noble metals acting as the base of the hitherto known mercury contacts are prone to forming intermediate phases and chemical compounds with the mercury, which matter accumulates at the contact junction and eventually affects the electric and dynamic characteristics of the mercury contact, and, hence, its reliability and durability.
The hitherto known mercury contact having iron for its solid metal base is produced by periodic dipping of the pre-coated iron base into a sodium amalgam through either a weak solution of a mineral acid or water.
(See, for instance, "Working with Mercury under Laboratory and Production Conditions" by P. P. Pugatchevitch, in Russian, NAUKA Publishers, Moscow, 1972, p. 183).
Iron, as well as nickel and the metals of the chromium subgroup practically would not react with mercury. However, these metals are thermodynamically unstable on account of their being electrochemically active, which activity is significantly enhanced by contact with mercury featuring a high positive potential.
Consequently, the contact junction is not resistant against electrochemical processes resulting in either partial or complete lack of adhesion between the solid metal and mercury. The probability and intensity of these processes are dependent on the quality of the initial wetting of the solid metal with mercury.
The hitherto known method would not provide for adequately wetting the surface of the above mentioned solid metals with mercury, on account of microcavities left in most cases at the contact junction under the mercury film and containing an electrochemically active medium, e.g. the remains of acids, water and other electrolytes employed by the production process.
These microcavities act as the nuclei of degrading electrochemical processes affecting the stability and durability of the solid metal-mercury contact junction.
The necessity for suppressing these degrading electrochemical processes significantly complicates the technology of wetting the surface of the hard or solid metal with mercury, and of the manufacture of the contact.